Manufacture of artificial threads from cellulose esters or cellulose ethers



Patented Apr. 16, 1935 UNITED STATES PATENT OFFICE ETHER-S Paul Schlack,Berlin-Karlshorst, Germany, as

signor to Aceta G. in.

b. H., Lichtenberg, Germany, a corporation of Germany N Drawing.Application April 27, 1929, Serial No. 358,762. In Germany May 1, 1928 7Claims.

This invention relates to a process for the manufacture of artificialthreads from a solution of cellulose esters and ethers, according to thewet spinning process, and to the threads obtainable thereby. A furtherobject of the present invention is to provide an artificial silk of theclass mentioned above, having a dry tensile strength of 2 to 2.5 gramsper denier and more.

It is known in the manufacture of threads from cellulose esters orethers, according to the wet spinning process, to use a precipitatingbath which contains a salt having a swelling action upon the threadformed and which causes a retarding of the coagulation of the threads.Such salts are, for instance, sulfo cyanides, zinc halogenides, alkalimetal, salicylates and other salts with highly hydrated ions.

Fine threads spun in such a bath by the stretching-spinning process havea tensile strength of about 1.3 to 1.8 grams per denier, which exceedsthat of the threads usually obtainable by the dry spinning process tothe extent of about 25 to 30%.

However, when using a known precipitating bath of the kind mentioned inthe second paragraph of this specification, it easily occurs that theproduced fibers having originally a fine titer stick fast together andshow after drying a hard and brittle feel contrary to threads obtainedby the dry spinning process.

When operating according to my invention, threads are obtainable inwhich the individual fine fibers are completely separated from oneanother; after drying, they show an excellent soft feel and an agreeableluster. The latter may be modified by varying the spinning conditions bysuitable additions to the spinning bath. Furthermore, the tensilestrength of the threads is essentially increased up to 2.5 grams perdenier and more.

According to my invention a precipitating bath is used which containsbesides such a salt as retards the coagulation of the threads an organicpolymerized substance of high molecular weight, which is colloidlydispersed by water. As such a colloid I use, for instance, molasses,sulfite cellulose waste liquor, tanning substances, carbohydrates, suchas starch, dextrin, mucilage, gum, or protein-substances, such asgelatin, glue, casein, degraded glutin and the like; furthermore naturalresins, soluble synthetic resins, as for instance, the productsobtainable from aromatic sulionic acids and aldehydes. The quantity ofthese substances which I add to the precipitating bath may be variedwithin wide limits. Good results are obtainable, for instance, whenadding only 5 grams of the colloid compound per liter of theprecipitating bath. It is obvious that the result varies according tothe quantity and to the specific compound used, but the best result maybe easily determined by a simpleexperiment in each specific case. Iprefer to use as a particularly suitable colloid sulfite cellulose wasteliquor or a solution of a slightly degraded protein substance, forinstance, that of slightly degraded glutin (see Berichte der DeutschenChemischen Gesellschaft, vol. 35, page 2195).

The action of the spinning bath may be further modified by addinganother salt or other salts which have no or no considerable swellingaction upon the substance to be spun, for instance, calcium chloride,magnesium chloride, sodium acetate, ammonium nitrate, or mixturesthereof, or by adding a non-volatile or diflicultly volatile organicsubstance which has a swelling or dissolving action upon the celluloseproduct to be spun, for instance, a chlorohydrine, an ester or" apolyvalent alcohol, such as glycol monoacetate, monoacetine, triacetine,an ether of a polyvalent alcohol, such as glycol monomethyl-ether,glycol monoethylether and the like, a monoor polyvalent phenol, aketone, such as diacetone alcohol, cyclohexanone and its homologues.Instead of adding the swelling agent to the precipitating bath, I canadd it also partly or wholly to the solution of the cellulose ester orether which is pressed into the precipitating bath. In this case, ofcourse, the quantity of the swelling agent in the precipitating bath maybe considerably diminished.

The effect of my precipitating bath is not diminished by the fact that acertain amount of the solvent which is used in precipitating thespinning solution is introduced during the spinning process into theprecipitating bath, care must be taken, however, that the amount of thesolvent present in the precipitating bath does not become too large, anddoes not exceed about 9%. The maximum quantity depends on the quality ofthe dissolving agent and on the composition of the precipitating bathand will be easily ascertained from time to time by simple experiments.The manufacture of a uniform product on a large scale is, therefore,connected with no difficulties. Recovery of the solvent and thepreparation of the precipitating bath is particularly simple if theacetyl cellulose is dissolved in a single solvent, for instance,acetone.

I prefer to carry out my process in such a way that the length of thethreads immersed in the precipitating bath is about 30 cm., but it maybe shortened, for example to 15 cm. or extended to 60 cm., or more. Thethreads are then collected on a bobbin or in a spinning centrifuge inthe usual manner.

The threads may be subjected to a stretching procedure in any knownmanner during. the precipitating step or after their removal from thebath, that is, between the coagulating bath and the collecting device.The stretching may be accomplished either by providing a substantialdistance between the bath and the collecting device or by leading thethreads over rods or rolls arranged in the bath or between the bath andthe collecting device.

The speed of spinning may be varied within wide limits. It depends onthe length of immersion of the thread in the precipitating bath, on theopening of the nozzle, on the concentration of the spinning solution, onthe quantity of the spinning solution conveyed by the spinning pump tothe nozzle, etc. The temperature of the precipitating bath and of thespinning solution may also be varied within certain limits, as, forinstance, from to 40 C. I prefer to keep them at room temperature, thatis to say, at about C.

When using a bath according to my invention, it is easy to produceartificial silk threads from acetyl cellulose having a. dry tensilestrength of 2 to 2.5 grams per denier and more, that is to say, at leastdouble the strength of the products which are obtainable by spinning inaccordance with the usual dry spinning process.

The following examples are given to illustrate my invention withoutlimiting it to the specific details given therein:

Example 1.-A solution of 22 per cent. strength of acetyl cellulose inacetone is forced through spinning nozzles having bores of 0.5 mm.diameter into a precipitating bath which contains per liter 200 grams ofammonium sulfocyanide and 550 grams of purified sulfite cellulose wasteliquor of specific gravity 1.25. The temperature of the bath should beabout 20 C. and the length of immersion about 30 centimeters. Thecontent of acetone in the bath may vary within wide limits, for example,between 1 and 9 per cent. The thread which is spun at a speed of about15 to 20 meters per minute is washed with water on its way to the spoolor to the spinning box. A silk is obtained with a nearly circularsection, with an individual titer of l to 2 deniers and a dry tensilestrength from 2 to 3 grams per denier.

Example 2.-The operation is carried out as described in Example 1, but aprecipitating bath is used containing instead of the sulfite cellulosewaste liquor per liter 400 grams of molasses residue of specific gravity1.33. By molasses residue the final molasses is meant, that is to say,the product which remains after removing the crystallized portions ofsugar.

Example 3.The operation is as described in Example 1, but there aresubstituted for the sulfite cellulose waste liquor about 500 grams of anaqueous solution of degraded glutin of specific gravity 1.25 per literof the precipitating bath.

Example 4.-A solution consisting of 20 parts of acetyl cellulose, 2parts of ammonium sulfocyanide, 4 parts of water and 74 parts ofacetone, is spun into a precipitating bath which contains per liter 500grams of a soluiton of degraded glutin having the specific gravity 1.25and 40 grams of ammonium sulfocyanide. As mentioned in the precedingexamples a silk is obtained with a section approximating to a circularform, the strength of which however is somewhat smaller and amounts toabout 2 grams per denier.

Example 5.A spinning solution consisting of 20 parts of an acetylcellulose, containing chemically bound 54.5% of acetic acid in 80 partsof acetone is spun into a precipitating bath which contains:

1 part of the glutin solution mentioned in Example 4,

1.2 parts of ammonium sulfocyanate,

1 part of sodium acetate,

1 part of calcium chloride and 3.5 parts of water.

The temperature of the precipitating bath should be kept at 20, thelength of immersion of the thread is about 30 centimeters and thedrawing speed about -30 meters per minute. A silk is obtained withnearly circular section, good luster and a dry tensile strength of 2.5to 3.5 grams per denier.

Having now particularly described the nature of my said invention and inwhat manner the same is to be performed, I declare that what I claim is:

1. In the manufacture of artificial silk from organic cellulosederivatives the steps which comprise extruding a solution of an organiccellulose derivative dissolved in an organic solvent into aprecipitating bath comprising besides an agent capable of exerting aswelling action on the cellulose derivative an organic colloid solublein said precipitating bath,-and stretching the freshly precipitatedthreads.

2. In the manufacture of artificial silk from organic cellulosederivatives the steps which comprise extruding a solution of a celluloseacetate into a precipitating bath comprising besides an agent capable ofexerting a swelling action on the cellulose acetate an organic colloidsoluble in said precipitating bath, and stretching the freshlyprecipitated threads.

3. In the manufacture of artificial silk from organic cellulosederivatives the steps which comprise extruding a solution of a.cellulose acetate into an aqueous precipitating bath comprising besidesan agent capable of exerting a swelling action on the cellulose acetatea colloid soluble in said precipitating bath, and stretching the freshlyprecipitated threads.

4. In the manufacture of artificial silk from organic cellulosederivatives the steps which comprise extruding a solution of a celluloseacetate into an aqueous precipitating bath comprising besides an agentcapable of exerting a swelling action on the cellulose acetate apolymeric carbohydrate soluble in said precipitating bath, andstretching the freshly precipitated threads.

5. In the manufacture of artificial silk from organic cellulosederivatives the steps which comprise extruding a solution of a celluloseacetate into an aqueous precipitating bath comprising besides an agentcapable of exerting a swelling action on the cellulose acetate a proteinsoluble in said precipitating bath, and stretching the freshlyprecipitated threads.

6. In the manufacture of artificial silk from organic cellulosederivatives the steps which comprise extruding a solution of a celluloseacetate into an aqueous precipitating bath comprising besides ammoniumsulfo cyanide, degraded glutin, and stretching the freshly precipitatedthreads.

7. In the manufacture of artificial silk from organic cellulosederivatives the steps which comprise extruding a solution of a celluloseacetate into an aqueous precipitating bath comprising besides ammoniumsulfo cyanide, sulfite cellulose waste liquor, and stretching thefreshly precipitated threads.

PAUL SCHLACK.

